Chapter 19Chapter 19

Chemical BondsChemical Bonds

Lesson 3 Part 2Lesson 3 Part 2

Binary Ionic CompoundsBinary Ionic Compounds

• Binary ionic compounds. – composed of two elements.

• Before you can write a formula, – you must have all the needed

information at your fingertips.

– elements are involved and what number of electrons they lose, gain, or share

Binary Ionic CompoundsBinary Ionic Compounds

• Oxidation number – how many electrons an atom has

gained, or shared to become stable.– ionic compounds the oxidation number

is the same as the charge on the ion.

• For example – sodium ion has a charge of 1+ and an

oxidation number of 1+.

Oxidation NumbersOxidation Numbers

• The elements – more than one oxidation

number.

• Naming compounds – oxidation number is

expressed in the name with a roman numeral

– the oxidation number of iron in iron (III) oxide is 3++..

Compounds Are NeutralCompounds Are Neutral

• Writing formulas – the individual ions in a compound carry

charges, the compound itself is neutral.– must have the right number of positive

ions and the right number of negative ions so the charges balance.

Compounds Are NeutralCompounds Are Neutral

• Calcium fluoride – calcium ion has a charge of 2+ and a

fluoride ion has a charge of 1 −.

– two fluoride ions for every calcium ion

• C2+ F1- Cris-cross and drop– charges cancel and the compound is

neutral with the formula CaF2.

Writing FormulasWriting Formulas

1. Write the symbol of the element which has the positive oxidation number or charge

2. Write the symbol of the element or polyatomic ion with the negative oxidation number.

3. The charge (without the sign) of one ion becomes the subscript of the other ion.

Naming FormulasNaming Formulas

1. Write the name of the positive ion.

2. Check to see if the positive ion is capable of forming more than one oxidation number. If it is, determine the oxidation number of the ion from the formula of the compound.

Writing Names Writing Names

3. Write the charge of the positive ion using roman numerals in parentheses after the ion’s name. If the ion has only one possible oxidation number, proceed to step 4

Writing NamesWriting Names

4.4. Write the root name of the negative ion. The root is the first part of the element’s name.

5. Add the ending -ide to the root. The table lists several elements and their -ide counterparts.

Writing Names Writing Names

• Subscripts – do not become part of the name for

ionic compounds– can be used to help determine the

charges of the metals that have more than one positive charge

Examples of naming for multiple charges

Element Cation Preferred Name

Other Name

copper Cu+ copper (I) cuprous

Cu2+ copper (II) cupric

iron Fe2+ Iron (II) Ferrous

Fe3+ Iron (III) Ferric

Lead Pb2+ Lead (II) Plumbous

Pb4+ Lead (IV) plumbic

Mercury Hg22+ Mercury (I) Mercurous

Hg2+ Mercury (II) Mercuric

Tin Sn2+ Tin (II) Stannous

Sn4+ Tin (IV) Stannic